JP4784260B2 - Distributed data storage method, terminal, and program - Google Patents

Description

  The present invention relates to a data distributed storage method, a terminal, and a program. In particular, in a mobile terminal such as a mobile phone, it is suitable for concealing and holding data without reducing operability.

  As mobile terminals become widespread, it is assumed that data stored in the mobile terminal leaks due to loss or theft of the mobile terminal. In recent years, mobile phones often have an electronic payment function such as a credit card, and data or personal information that requires confidentiality is stored in mobile terminals. In such a situation, the portable terminal attempts to prevent unauthorized use by a third party by encrypting and storing these data using a key such as a password.

  The encrypted data can be stored in a storage device inside the mobile terminal, and further stored in an external storage device such as a remote server or a USB (Universal Serial Bus) memory. However, when the encrypted data leaks, it is possible to detect the matching key by taking a certain amount of time with a computer that performs high-speed computation. That is, when data is stored and managed in one device, the data may be restored if the encryption resistance is not very high.

  On the other hand, there is an encryption method called a secret sharing method. In the secret sharing method, the original data is encrypted, the encrypted data is divided, and the divided data (share) is managed in different places. Here, unless the specific number of divided data pieces are prepared, the original data cannot be decoded. It is configured so that the original data cannot be decrypted when the encrypted data leaks less than a specific number.

  However, managing a plurality of pieces of divided data with different servers on the network is effective in terms of encryption resistance, but is inconvenient in terms of cost. For example, if a cellular phone that is widely spread is targeted, the cost for accumulating and managing the data accumulated in the cellular phone by a plurality of servers must be enormous.

  On the other hand, according to the prior art, when data is stored and managed by one server, there is a problem that encryption resistance is weakened because encryption depends only on a key such as a password.

  Accordingly, an object of the present invention is to provide a distributed data storage method, a terminal, and a program that can ensure extremely high encryption resistance for original data of a terminal only by providing one external storage device. And

According to the present invention, in a distributed data storage method in a terminal connectable to an external storage device,
For data encryption,
Dividing the original data into first local data and first remote data, and determining the length of the first remote data according to the communication speed with the external storage device;
A second step of generating the second local data by encrypting the first remote data from the first local data as a key;
A third step of transmitting and storing the first remote data to an external storage device;
And a fourth step of storing the second local data in the local data storage unit.

According to another embodiment of the distributed storage method of the present invention,
It is also preferable that the first step divides the original data based on a secret sharing method.

Furthermore, according to another embodiment of the distributed storage method of the present invention,
For data decryption,
A fifth step of acquiring second local data from the local data storage unit;
A sixth step of receiving first remote data from an external storage device;
A seventh step of generating first local data by decrypting the first remote data from the second local data as a key;
It is preferable that the method further includes an eighth step of combining the first local data and the first remote data to generate original data.

Furthermore, according to another embodiment of the distributed storage method of the present invention,
In the first step, the original data is compressed to generate original compressed data, the original compressed data is divided,
As an eighth step, it is also preferable to decompress the original compressed data to generate the original data.

Furthermore, according to another embodiment of the distributed storage method of the present invention,
And scrambling the first remote data between the first step and the second step to generate the second remote data;
The second step generates second local data from the first local data by using the second remote data as a key and encrypting by exclusive OR of a bit string for each second remote data length,
The third step transmits the second remote data to the external storage device and accumulates it,
The sixth step receives the second remote data from the external storage device,
The seventh step generates the first local data from the second local data by using the second remote data as a key and decrypting by exclusive OR of the bit strings for each second remote data length,
Preferably, the second remote data is descrambled between the seventh step and the eighth step to generate the first remote data.

Furthermore, according to another embodiment of the distributed storage method of the present invention,
For the first step, an allowable communication time is predetermined to obtain remote data from the external storage device,
Calculate the maximum data length that satisfies the allowable communication time based on the communication speed with the external storage device,
The length of the remote data is preferably determined to be equal to the length of the local data at the maximum and not more than the maximum data length.

According to the present invention, in a terminal that can be connected to an external storage device for distributed storage of data,
For data encryption,
Data dividing means for dividing the original data into first local data and first remote data, and determining the length of the first remote data according to the communication speed with the external storage device;
Encryption means for generating second local data by encrypting the first remote data from the first local data as a key;
Remote data transmission means for transmitting and storing the first remote data to an external storage device;
And local data storage means for storing second local data.

Also, according to another embodiment of the terminal of the present invention,
The data dividing means preferably divides the original data based on the secret sharing method.

Furthermore, according to another embodiment of the terminal of the present invention,
For data decryption,
Remote data receiving means for receiving first remote data from an external storage device;
Decryption means for decrypting the first remote data as a key from the second local data acquired from the local data storage means to generate the first local data;
It is also preferable to further include data synthesizing means for synthesizing the first local data and the first remote data to generate original data.

Furthermore, according to another embodiment of the terminal of the present invention,
Data compression means for compressing the original data to generate original compressed data, and notifying the original compressed data to the data dividing means;
It is also preferable to have data decompression means for receiving the original compressed data from the data synthesizing means and decompressing the original compressed data to generate original data.

Furthermore, according to another embodiment of the terminal of the present invention,
Scrambling means for generating first remote data by scrambling the first remote data notified from the data dividing means, and notifying the second remote data to the remote data transmitting means;
Further comprising: descrambling means for descrambling the second remote data notified from the remote data receiving means to generate first remote data, and notifying the decoding means of the first remote data;
The encryption means generates second local data by encrypting by exclusive OR of a bit string for each second remote data length using the second remote data as a key from the first local data,
The decrypting means preferably generates the first local data from the second local data using the second remote data as a key and decrypting the second remote data by exclusive OR of a bit string for each second remote data length.

Furthermore, according to another embodiment of the terminal of the present invention,
The data dividing means has a predetermined allowable communication time for acquiring remote data from the external storage device,
Calculate the maximum data length that satisfies the allowable communication time based on the communication speed with the external storage device,
The length of the remote data is preferably determined to be equal to the length of the local data at the maximum and not more than the maximum data length.

According to the present invention, in a program for functioning a computer mounted on a terminal connectable to an external storage device for distributed storage of data,
For data encryption,
Data dividing means for dividing the original data into first local data and first remote data, the length of the first remote data being determined according to the communication speed with the external storage device;
Encryption means for generating second local data by encrypting the first remote data from the first local data as a key;
Remote data transmission means for transmitting and storing the first remote data to an external storage device;
The computer is caused to function as local data storage means for storing the second local data.

According to another embodiment of the program of the present invention,
For data decryption,
Remote data receiving means for receiving first remote data from an external storage device;
Decryption means for decrypting the first remote data as a key from the second local data acquired from the local data storage means to generate the first local data;
It is also preferable that the computer further function as data synthesizing means for synthesizing the first local data and the first remote data to generate original data.

  According to the present invention, it is possible to ensure extremely high encryption resistance with respect to original data of a terminal only by providing one external storage device.

  According to the present invention, since the encryption key is created from the original data, the encryption key is different each time and the encryption resistance is increased. Also, by using the secret sharing method, the original data cannot be decrypted unless the local data and the remote data are aligned. By making the length of the remote data equal to the length of the local data at most, the approximate effect of Burnham encryption can be obtained. Furthermore, since the length of the remote data is determined according to the communication speed with the external storage device, the length R of the remote data cannot be grasped, and the encryption resistance can be further enhanced. Further, by compressing the original data, it is possible to prevent the regularity of the bit string (whole 8 bits) of the original data and to improve the encryption resistance. Furthermore, since the length of the remote data can be determined in consideration of the allowable communication time, the immediacy of the terminal 1 can be improved. Thus, according to the present invention, even if either local data or remote data is leaked to an unauthorized third party, the original compressed data including the other data cannot be decoded.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a flowchart for encryption in the present invention.

(S101) The original data is compressed. The compression algorithm may be an existing known method.

  The reason for compressing the original data first is not only to reduce the amount of data but also to increase the encryption resistance (the amount of calculation for decrypting the encryption). Usually, since there are many original data having a certain regularity (for example, text information in 7-bit units), even encrypted data may have a certain regularity (period). It can be said that encrypted data having a certain regularity has low encryption resistance. By compressing the original data, regularity of the bit string of the original data (all 8 bits) can be eliminated, and the encryption resistance can be increased.

(S102) The original compressed data is divided into first local data and first remote data based on a secret sharing scheme (SSS). At this time, the length of the first remote data is determined according to the communication speed with the external storage device.

  Specifically, first, the original compressed data is divided into a plurality of elements, and these elements are randomly allocated to two tally (local data and remote data). At this time, the arrangement of elements is recorded in the sorting table. The distribution table includes the number of divisions, the length of original compressed data, distribution information, and the like. For example, a sequence number can be assigned to an element in order, and a tally identification code can be assigned to each sequence number.

  The secret sharing method is a technique used for electronic tally, and the original data can be restored by dividing the original data into a plurality of divided data and collecting a specific number of the divided data. This is a technique for avoiding that when divided data is stored in different remote servers, the original data cannot be restored due to the server being down.

  Specifically, in the secret sharing method, the original data can be restored by dividing the original data into N pieces of divided data and collecting any K (≦ N) pieces of shared data. However, the original data cannot be restored with any K-1 divided data out of N. Such a secret sharing method is also referred to as a (K, N) threshold method.

  On the other hand, according to the present invention, the original compressed data is divided by using the secret sharing method of the (2, 2) threshold method. This is because the original compressed data is divided into N = 2 and cannot be restored unless K = 2 (= N) pieces of divided data are collected. That is, it means that the original compressed data cannot be decoded with any one piece of divided data.

  The two tallys are called local data and remote data. Local data is a tally stored in the storage device of the terminal 1, and remote data is a tally stored in the storage device of the remote server 2.

  As a further characteristic feature of the present invention, the length R of the remote data is equal to or less than the length L of the local data (half the length D of the original compressed data) and the network communication band (transmission speed). It becomes variable according to the above. In particular, when the network communication band is narrow (transmission speed is slow), the remote data length R is shortened, and when the network communication band is wide (transmission speed is fast), the remote data length R is lengthened. However, the length R of the remote data is at most equal to the length L of the local data.

  According to the present invention, since the network communication band varies depending on the location of the terminal 1, the length R of the remote data changes automatically each time. Accordingly, not only the user of the terminal 1 but also the third party cannot grasp the length R of the remote data. If the length R of the remote data cannot be grasped, the original compressed data cannot be decrypted, which also contributes to increase the encryption resistance.

Specifically, the length R of the remote data is determined by the following method in consideration of the decoding time in the terminal 1. The decryption time is restricted by the decryption processing time in the terminal 1 and the communication time for downloading the encrypted data from the server. As for the communication time, a relational expression between the amount of encrypted data transferred and the transmission speed is established as follows.
Communication time = amount of encrypted data / transmission speed

According to the present invention, the allowable communication time for acquiring remote data from an external storage device (for example, a remote server) is determined in advance. Then, the maximum data length that satisfies the allowable communication time can be calculated based on the communication speed with the remote server. Therefore, the length of the remote data is determined to be equal to the length of the local data at the maximum and not more than the maximum data length.
Maximum amount of encrypted data = allowable communication time x transmission speed

Table 1 shows the amount of encrypted data with respect to the transmission rate. If the allowable communication time is 3 seconds, for example, the following occurs.

(S103) The remote data is scrambled to generate remote data 2 (length R2). The scramble algorithm may be a well-known one or a variable parameter that can be given. A random bit string having a long regularity (period) can be derived by scrambling already compressed remote data. Also, it is necessary to scramble the remote data in order to store it in the remote server. The scramble algorithm needs to have at least reversibility.

  Here, a hash function can be used as the scramble algorithm. However, since the hash function is not a reversible algorithm, the original data must be stored in the remote server.

(S104) The local data is encrypted with the remote data 2, and the local data 2 (length L2) is generated.

  An example of encryption here is Vernam encryption. With Burnham encryption, if the original data and the key length are equal and the key is a sufficient random number sequence, the key is exclusive ORed (XOR) with the original data. It is an algorithm that has been proven not to be decipherable only from digitized data.

  If the length of the remote data is shorter than the length of the local data, the remote data can be applied to the local data one by one in block cipher and XORed.

  According to the present invention, in order to construct approximate Vernam encryption, the length L of the local data and the length R of the remote data are made equal to each other at the maximum. As a key for encrypting the local data L, it can be said that the scrambled remote data 2 is a sufficient random number sequence. Then, if the exclusive OR is performed on the local data with the remote data 2 which is a key of a sufficient random number sequence, the local data is approximately the Burnham cipher. Therefore, the effect is also approximately impossible to decrypt only from the encrypted data.

  In addition, as a feature of the present invention, since the encryption key is created from the original compressed data, the encryption key is different every time, and there is an effect that the encryption resistance is increased.

(S105) The remote data 2 is transmitted to the remote server 2 via the network.

(S106) The terminal 1 stores the local data 2 in the local data storage unit. At this time, the URI (Uniform Resource Identifier: RFC3986) of the remote server 2 in which the remote data 2 is stored is stored in the local data storage unit in association with the local data 2.

  FIG. 2 is a flowchart for decoding in the present invention.

(S201) The terminal 1 searches and extracts the local data 2 of the data to be decoded from the local data storage unit.

(S202) The terminal 1 takes out the URI together with the local data 2 from the local data storage unit. The terminal 1 makes an inquiry to the remote server 2 via the network based on the URI, and receives the remote data 2 of the data to be decrypted from the remote server 2.

(S203) The local data 2 is decrypted using the remote data 2 as a key. Specifically, an exclusive OR (XOR) is performed on the local data 2 for each block of the remote data 2.

(S204) The remote data 2 is descrambled to derive the remote data.

(S205) The elements included in the local data and the elements included in the remote data are combined according to the table information and decoded into the original compressed data.

(S206) The original compressed data is decompressed and the original data is derived.

  FIG. 3 is a functional configuration diagram of the system according to the present invention.

  According to FIG. 3, the terminal 1 is connected to the remote server 2 via a network. However, the remote data 2 may be an external storage device such as a USB memory. That is, the remote data 2 may be stored outside the terminal 1.

  Each function of the terminal 1 described below may be realized by causing the computer to execute the program. Such a program is preferably implemented as a device driver.

  The terminal 1 uses a data compression unit 101, a data division unit 102, a scramble unit 103, an encryption unit 104, a remote data transmission unit 105, a local data storage unit 106, and a communication band detection for encryption. Part 112. The terminal 1 further includes a remote data receiving unit 107, a descrambling unit 108, a decoding unit 109, a data synthesis unit 110, and a data decompression unit 111 for decoding.

  The data compression unit 101 compresses the original data as in S101 described above.

  As in S102 described above, the data dividing unit 102 divides the original compressed data notified from the data compressing unit 101 into first local data and first remote data based on the secret sharing method. At this time, the length of the first remote data is determined according to the communication speed with the external storage device detected by the communication band detection unit 112.

  The scramble unit 103 scrambles the remote data notified from the data dividing unit 102 to generate remote data 2 as in S103 described above.

  The encryption unit 104 encrypts the local data notified from the data dividing unit 102 with the remote data 2 notified from the scramble unit 103 to generate local data 2 as in S104 described above.

  The remote data transmission unit 105 transmits the remote data 2 notified from the scramble unit 103 to the remote server 2 via the network as in S105 described above.

  The local data storage unit 106 stores the local data 2 notified from the encryption unit 104 as in S106 described above. Further, the local data 2 is output to the decoding unit 109 as in S201 described above.

  The remote data receiving unit 107 receives the remote data 2 of the data to be decrypted from the remote server 2 as in S202 described above.

  The descrambling unit 108 descrambles the remote data 2 to derive remote data as in S204 described above.

  The decrypting unit 109 decrypts the local data 2 using the remote data 2 as a key as in S203 described above.

  The data synthesizing unit 110 synthesizes the elements included in the local data and the elements included in the remote data according to the table information as in S205 described above, and decodes the original compressed data.

  The data decompression unit 111 decompresses the original compressed data and derives the original data as in S206 described above.

  The communication band detecting unit 112 detects a communication band (transmission speed) with the remote server 2 and notifies the data dividing unit 102 of the communication band information.

  As described above, according to the distributed data storage method, terminal, and program of the present invention, it is possible to ensure extremely high encryption resistance for the original data of the terminal only by providing one external storage device.

  According to the present invention, since the encryption key is created from the original data, the encryption key is different each time and the encryption resistance is increased. Also, by using the secret sharing method, the original data cannot be decrypted unless the local data and the remote data are aligned. By making the length of the remote data equal to the length of the local data at most, the approximate effect of Burnham encryption can be obtained. Furthermore, since the length of the remote data is determined according to the communication speed with the external storage device, the length R of the remote data cannot be grasped, and the encryption resistance can be further enhanced. Further, by compressing the original data, it is possible to prevent the regularity of the bit string (whole 8 bits) of the original data and to improve the encryption resistance. Furthermore, since the length of the remote data can be determined in consideration of the allowable communication time, the immediacy of the terminal 1 can be improved. Thus, according to the present invention, even if either local data or remote data is leaked to an unauthorized third party, the original compressed data including the other data cannot be decoded.

  The data in the present invention may be customer data stored in a mobile terminal, for example. Generally, customer data is stored in a server and is realized by referring to the server from a mobile terminal. According to the present invention, since encryption resistance is high, by storing a part of customer data as local data in a mobile terminal, it is possible to improve immediacy when referring to the data.

  The data in the present invention may be, for example, copyrighted music / movie content. In general, music / movie content is stored in a portable terminal, but there is a risk of unauthorized use by copying. As in the present invention, by associating the mobile terminal and the remote server, a part of these contents is accumulated in the mobile terminal, so that immediacy can be secured and unauthorized use of the contents can be prevented.

  According to the above-described various embodiments of the present invention, those skilled in the art can easily make various changes, modifications, and omissions in the technical idea and scope of the present invention. The above description is merely an example, and is not intended to be restrictive. The invention is limited only as defined in the following claims and the equivalents thereto.

It is a flowchart for the encryption in this invention. It is a flowchart for the decoding in this invention. It is a functional block diagram of the system in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Terminal 101 Data compression part 102 Data division part 103 Scramble part 104 Encryption part 105 Remote data transmission part 106 Local data storage part 107 Remote data reception part 108 Descramble part 109 Decoding part 110 Data composition part 111 Data decompression part 112 Communication band Detector 2 Remote server

Claims (12)

In a distributed storage method of data in a terminal connectable with an external storage device,
For encryption of the data,
The terminal divides the original data into first local data and first remote data, and an allowable communication time is determined in advance for acquiring the first remote data from the external storage device; Calculating a maximum data length that satisfies the allowable communication time based on a communication speed with the storage device, and setting the length of the first remote data equal to the length of the first local data at the maximum, and A first step of determining to be less than or equal to the maximum data length ;
A second step in which the terminal encrypts the first remote data from the first local data as a key to generate second local data;
A third step in which the terminal transmits and accumulates the first remote data to an external storage device;
And a fourth step in which the terminal stores the second local data in a local data storage unit.   The method according to claim 1, wherein the first step divides the original data based on a secret sharing method. For decoding the data,
A fifth step in which the terminal acquires the second local data from the local data storage unit;
A sixth step in which the terminal receives the first remote data from the external storage device;
A seventh step for the terminal to generate the first local data by decrypting the second remote data using the first remote data as a key;
The said terminal further has an 8th step which synthesize | combines the said 1st local data and the said 1st remote data, and produces | generates the said original data, The Claim 1 or 2 characterized by the above-mentioned. A distributed storage method for data. In the first step, the original data is compressed to generate original compressed data, the original compressed data is divided,
4. The distributed data storage method according to claim 3, wherein the original data is generated by decompressing the original compressed data as an eighth step. And scrambling the first remote data to generate second remote data between the first step and the second step;
The second step generates second local data from the first local data by encrypting by exclusive OR of a bit string for each second remote data length using the first remote data as a key. And
In the third step, the second remote data is transmitted to and stored in the external storage device,
The sixth step receives the second remote data from the external storage device,
The seventh step generates the first local data from the second local data by decrypting the second remote data as a key by exclusive OR of a bit string for each second remote data length. And
5. The data according to claim 3, wherein first remote data is generated by descrambling the second remote data between the seventh step and the eighth step. 6. Distributed storage method. In a terminal that can be connected to an external storage device for distributed storage of data,
For encryption of the data,
An allowable communication time is determined in advance to divide the original data into first local data and first remote data, and acquire the first remote data from the external storage device. A maximum data length that satisfies the allowable communication time is calculated based on a communication speed between the first remote data and the length of the first remote data equal to the length of the first local data at the maximum, and Data dividing means for determining to be :
Encryption means for generating second local data by encrypting the first remote data from the first local data as a key;
Remote data transmission means for transmitting and storing the first remote data to an external storage device;
And a local data storage means for storing the second local data. The terminal according to claim 6 , wherein the data dividing unit divides the original data based on a secret sharing method. For decoding the data,
Remote data receiving means for receiving the first remote data from the external storage device;
Decryption means for decrypting from the second local data acquired from the local data storage means using the first remote data as a key to generate the first local data;
The first by combining said local data first remote data terminal according to claim 6 or 7, further comprising a data combining means for generating the original data. Data compression means for compressing the original data to generate original compressed data, and notifying the original compressed data to the data dividing means;
9. The terminal according to claim 8 , further comprising: a data decompressing unit that receives the original compressed data from the data synthesizing unit and decompresses the original compressed data to generate the original data. Scrambling means for generating the second remote data by scrambling the first remote data notified from the data dividing means, and notifying the remote data transmission means of the second remote data;
A descrambling means for generating the first remote data by descrambling the second remote data notified from the remote data receiving means, and notifying the decoding means of the first remote data; Have
The encryption means encrypts the first local data by using the second remote data as a key and performs exclusive OR of a bit string for each second remote data length to generate second local data. ,
The decoding means generates the first local data by decoding the second local data by using an exclusive OR of a bit string for each second remote data length using the second remote data as a key. The terminal according to claim 8 or 9 , characterized in that In a program for functioning a computer mounted on a terminal connectable to an external storage device for distributed storage of data,
For encryption of the data,
An allowable communication time is determined in advance to divide the original data into first local data and first remote data, and acquire the first remote data from the external storage device. A maximum data length that satisfies the allowable communication time is calculated based on a communication speed between the first remote data and the length of the first remote data equal to the length of the first local data at the maximum, and the maximum data length Data dividing means for determining to be :
Encryption means for generating second local data by encrypting the first remote data from the first local data as a key;
Remote data transmission means for transmitting and storing the first remote data to an external storage device;
A program for causing a computer to function as local data storage means for storing the second local data. For decoding the data,
Remote data receiving means for receiving the first remote data from the external storage device;
Decryption means for decrypting from the second local data acquired from the local data storage means using the first remote data as a key to generate the first local data;
The first by combining said local data first remote data, the program according to claim 1 1, characterized in that the computer is further caused to function as a data synthesizing means for generating original data.

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